The problem is how to graphically emphasize a particular path or paths in a representation of a diagram such as a data flow diagram. A data flow diagram is a graphical representation of the flow of data through an information system. Data flow diagrams include stages or nodes connected by links or lines. A data flow diagram in a path design tool may include a path query which identifies a path through data stages. A problem is how to emphasize such a path through the diagram.
There are guidelines set by the United States Government under Section 508 of the Rehabilitation Act of 1973 regarding the accessibility of and use of information and data by Federal employees with disabilities. Section 508 also requires that individuals with disabilities, who are members of the public seeking information or services from a Federal agency, have access to and use of information and data.
Most of the specifications of the guidelines for software pertain to usability for people with vision impairments. For example, one provision requires alternative keyboard navigation, which is essential for people with vision impairments who cannot rely on pointing devices, such as a mouse. Other provisions address animated displays, color and contrast settings, flash rate, and electronic forms, among others.
One of the guidelines for software applications and operating systems is that “Color coding shall not be used as the only means of conveying information, indicating an action, prompting a response, or distinguishing a visual element” (Section 1194.21(i)).
The requirements of emphasizing a path in a diagram such as a data flow diagram can be summarised as the following:
i) An observer must be able to differentiate between the nodes not in the path from the nodes that are in the path;
ii) An observer must be able to read all information on nodes in the data flow diagram, whether emphasized or not, and
iii) A colour must not by itself be used to convey information.
Current solutions for emphasizing a path through a data flow diagram include the following:
1) Colour all nodes in the path. This means point (ii) above fails since once coloured, the graphical information on a node cannot be read. Point (iii) is also not met and would fail Section 508 compliance.
2) Do not display any nodes that are not in the path, but this again fails point (ii).
3) Produce a textual report, but this looses the visual representation of the data flow diagram.